This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Slit/Robo signaling has been established as a novel pathway that modulates angiogenesis. Our recent studies found that heparan sulfate critically modulates Slit3/Robo pathway-mediated angiogenesis. In this collaborative study we aim to elucidate the mechanism of Slit/Robo signaling in angiogenesis, and to elucidate the fine structure on heparan sulfate that is required to modulate Slit3/Robo signaling in angiogenesis.